Dextromethorphan (racemethorphan), 3-methoxy-17-methylmorphinan, is disclosed in the Merck Index. 10th edition (1983), M. Windholz, ed., No. 8009, p. 1170; it is disclosed to be an antitussive agent.
Dextromethorphan hydrobromide is used extensively as an antitussive agent in commercial products as disclosed in the Physician's Desk Reference for Nonprescription Drugs, 11th Edition (1990), E. R. Barnhardt, pub., p. 306, and in Physician's Desk Reference, 44th Edition (1990), E. R. Barnhardt, pub., p. 309: Bayer Children's Cough Syrup by Glenbrook, Benylin DM by Parke-Davis, Benylin Expectorant by Parke-Davis, Cerose-DM by Wyeth-Ayerst, Cheracol D Cough Formula by Upjohn, Cheracol Plus Head Cough/Cold Formula by Upjohn, Cough Formula Comtrex by Bristol-Myers Products, Comtrex Multi-Symptom Cold Reliever Tablets/Caplets/Liquid/Liquigels by Bristol-Myers Products, Contac Cough Formula by SmithKline Consumer, Contac Cough & Sore Throat Formula by SmithKiline Consumer, Contac Jr. Children's Cold Medicine by SmithKline Consumer, Contac Nighttime Cold Medicine by SmithKline Consumer, Contac Severe Cold Formula Caplets by SmithKline Consumer, Dimacol Caplets by Robins, Dorcol Children's Cough Syrup by Sandoz Consumer, Hold by SmithKline Beecham, Naldecon DX Adult Liquid by Bristol Laboratories, Naldecon DX Children's Syrup by Bristol Laboratories, Naldecon DX Pediatric Drops by Bristol Laboratories, Naldecon Senior DX Cough/Cold Liquid by Bristol Laboratories, Novahistine DMX by Lakeside Pharmaceuticals, Pediacare Cough-Cold Formula Liquid and Chewable Tablets by McNeil Consumer Products, Pediacare Night Rest Cough-Cold Formula Liquid by McNeil Consumer Products, Robitussin Night Relief by Robins, Robitussin-CF by Robins, Robitussin-DM by Robins, Scot-Tussin Sugar-Free DM Cough & Cold Medicine by Scot-Tussin, Snaplets-DM by Baker Cummins Pharmaceuticals, Snaplets-Multi by Baker Cummins Pharmaceuticals, St. Joseph Cough Suppressant for Children by Plough, St. Joseph Nighttime Cold Medicine by Plough, Sucrets Cough Control Formula by SmithKline Beecham, Sudafed Cough Syrup by Burroughs Wellcome, Triaminic Night Light by Sandoz Consumer, Triaminic-DM Syrup by Sandoz Consumer, Triaminicol Multi-Symptom Cold Tablets by Sandoz Consumer, Triaminicol Multi-Symptom Relief by Sandoz Consumer, Tylenol Cold Medication Caplets and Tablets by McNeil Consumer Products, Tylenol Cold Medication Liquid by McNeil Consumer Products, Tylenol Cold Medication No Drowsiness Formula Caplets by McNeil Consumer Products, Vicks Children's Cough Syrup by Richardson-Vicks, Inc., Vicks Children's NyQuil by Richardson-Vicks, Inc., Vicks Cough Silencers Cough Drops by Richardson-Vicks, Inc., Vicks Daycare Daytime Colds Medicine Caplets by Richardson-Vicks, Inc., Vicks Daycare Multi-Symptom Colds Medicine Liquid by Richardson-Vicks, Inc., Vicks Formula 44 Cough Control Discs by Richardson-Vicks, Inc., Vicks Formula 44 Cough Medicine by Richardson-Vicks, Inc., Vicks Formula 44D Decongestant Cough Medicine by Richardson-Vicks, Inc., Vicks Formula 44M Multi-Symptom Cough Medicine by Richardson-Vicks, Inc., Vicks NyQuil Nighttime Colds Medicine-Original & Cherry Flavor by Richardson-Vicks, Inc., Vicks Pediatric Formula 44 Cough Medicine by Richardson-Vicks, Inc., Vicks Pediatric Formula 44 Cough & Colds Medicine by Richardson-Vicks, Inc., Vicks Pediatric Formula 44 Cough & Congestion Medicine by Richardson-Vicks, Inc., Ambenyl-D Decongestant Cough Formula by Forest Pharmaceuticals, Bromarest DX Cough Syrup by Warner Chilcott, BromFed-DM Cough Syrup by Muro, Codimal DM by Central Pharmaceuticals, Dimetane-DX Cough Syrup by Robins, Guaifenesin w/D-Methorphan Hydrobromide Syrup by Lederle, Humibid DM Tablets by Adams, IoTuss-DM Liquid by Muro, Medi-Tuss DM by Warner Chilcott, Phenergan with Dextromethorphan by Wyeth-Ayerst, Poly-Histine DM Syrup by Bock, Quelidrine Syrup by Abbott, Rondec-DM Oral Drops by Ross, Rondec DM Syrup by Ross, Tusibron-DM by RAM Laboratories, Tussar DM by Rorer Pharmaceuticals, and Tussi-Organidin DM Liquid by Wallace. Delsym Cough Suppressant Syrup by McNeil Consumer contains dextromethorphan polistirex as an antitussive agent. It is believed that all of the above commercial products containing dextromethorphan are included in compositions at about neutral pH or lower.
Beckett, A. H., & E. G. Triggs, "Buccal Absorption of Basic Drugs and Its Application as an In Vivo Model of Passive Drug Transfer Through Lipid Membranes", Journal of Pharmaceutics and Pharmacology, Vol. 19 Supplement (1967), pp. 31S-41S, discloses that buccal absorption of a number of drugs is substantially increased from compositions having a higher pH, when such compositions are held and circulated in the mouth for 5 minutes. Dextromethorphan is not disclosed as one of those drugs tested in Beckett and Triggs. The disclosure of Beckett and Triggs would not be expected to be very pertinent to liquid products which are generally not held in the mouth but are swallowed quickly, or even to solid products such as lozenges which are allowed to dissolve in the mouth where the dissolution liquid is rapidly swallowed.
U.S. Pat. No. 4,892,877 issued to Sorrentino on Jan. 9, 1990, discloses liquid compositions for the treatment of coughs comprising both dextromethorphan and phenol, the compositions having a pH of 5-9. U.S. Pat. No. 4,427,681 issued to Munshi on Jan. 24, 1984, discloses thixotropic compositions for the treatment of coughs comprising both dextromethorphan and Avicel.RTM. RC-591. These patents are hereby incorporated by reference.